FIGS. 1 and 2 shows the arrangement of the bicycle wheel hub and freewheel gear cluster of a regular bicycle, comprised of a wheel hub 10, which comprises a longitudinal center through hole 11, a circular recess 16 at one end around the through hole 11, and a toothed hole 13 within the circular recess 16 around the through hole 11, a freewheel gear cluster 20, which consists of a set of gears 20, a hollow screw rod 30, a bearing assembly 40, a toothed locating block 14 with an inner thread 12 fastened to the toothed hole 13 of the hub 10, and a cap 15 mounted within the circular recess 16 to hold down the toothed locating block 14. The bearing assembly 40 comprises a coupling block 42 having inside teeth 41 meshed with the locating block 14 and disposed outside the cap 15, a ball bearing 43, a socket 44 with longitudinal ribs 45, a cup 46, and a cylindrical connecting rod 47. The coupling block 42 and the cup 46 are fastened together through screw joint and received inside the socket 44. The connecting rod 47 has one end inserted through the coupling block 42 and the cup 46 and terminating in an outward flange 48 stopped outside the cup 46, and an opposite end fastened to the inner thread 12 of the locating block 14 by screw joint. The freewheel gear cluster 20 is mounted around the longitudinal ribs 45 of the socket 44. The screw rod 30 is inserted through the longitudinal center through hole 11 of the hub 10 and the bearing assembly 40 and fastened to a quick release (not shown). This bicycle freewheel gear cluster mounting structure has drawbacks. Because the hub 10 must be made in integrity and the locating block 14 must be punched into the toothed hole 13 and then held down by the cap 15, the manufacturing and installation costs are high. When the locating block 14 is punched into engagement with the toothed hole 13, the center of the locating block 14 may be biased from longitudinal alignment with the longitudinal center through hole 11, causing the freewheel gear cluster 20 and the hub 10 not to have a common center. If the freewheel gear cluster 20 and the hub do not have a common center, the shifting of the gear will not be smoothly operated. Because the socket 44 and the freewheel gear cluster 20 are connected to the hub 10 at one side by the connecting rod 47 and the connecting rod 47 is fastened to the locating block 14, power is difficult to be uniformly distributed through the hub 10, and the freewheel gear cluster 20 may be forced to cause an eccentric effect. Furthermore, the connection between the connecting rod 47 and the locating block 14 is difficult to achieve and needs special techniques.